Deck resistance is not dependent on temperature. It's constant at every point across the curve. In fact, there should be ZERO or minimal resistance contributed by the deck. If there is more than minimal resistance from the deck, the way to compensate is to increase the starting resistance.
The only way to generate the black line is to make the deck resistance plus coil resistance temperature dependent as a whole system and develop your own TCR. If you think that's what's happening, then you've proven that the rta deck is faulty and you should follow @KenD's advice. Either fix what's wrong with it, or get rid of it.
I completely agree that the deck resistance doesn't change. Where we are missing each other is understanding how the mod works. That black line is not some mythical thing I imagined. That represents the values the mod is calculating as the target values it needs to hit at given temperatures. The mod itself is treating the whole coil+deck as a single system, but it doesn't know that only part of that system is variable (the coil) and part (the deck) is constant. The mod just takes the base reading of 0.245 and uses the TCR to generate that black line. And that black line is wrong.
Sorry to be stubborn about this, but honestly can you tell me where in my step-by-step of what's going on I missed something? I'll post it again here:
- Mod reads starting ohm of 0.245 (0.18 from coil, 0.065 from deck)
- I set my mod to a temp of 392F
- Mod uses TCR to calculate target resistance of 0.305858 (0.245 X 1.2484)
- Mod applies power until resistance reaches 0.305858